Electron microscopic identification of rotavirus group antigen with gold-labelled monoclonal IgG

The use of colloidal gold immunoelectron microscopy to diagnose varicella-zoster virus (VZV) infections by rapid discrimination between VZV, HSV-1 and HSV-2

Colloidal gold immunoelectron microscopy was used to diagnose rapidly 53 cases clinically suspected of varicella-zoster virus (VZV) infection and one special case selected from another study on typical herpes simplex virus (HSV) infections. The viruses were identified and subsequently typed within 2.5 h by a direct labelling test for VZV, and within 3.5 h by an indirect labelling test with monoclonal antibodies against HSV type 1 and type 2. The protein A purified IgG fraction of human anti-VZV immunoglobulins was adsorbed to colloidal gold particles, and the specificity of the gold-labelled antibodies was tested with several human and animal herpesviruses. Viral envelopes did not crossreact in the direct labelling test. However, an indirect labelling procedure revealed that a small fraction of the anti-VZV antibodies crossreacted with the cores of herpes simplex virus and pseudorabies virus (Aujeszky disease virus). Virus-infected cellular material taken from typical herpetic lesions was used directly without virus propagation for virus typing. All cases (N = 54) were analyzed without knowing the clinical description of the results of cytopathologic examination (Tzanck smear) and viral culture. Forty-four cases were identified as VZV; however, 5 of the supposed VZV infections were proved to be HSV infections. Although the viral culture of the one HSV case was HSV- and VZV-negative, colloidal gold labelling identified the case as VZV infection. In 16 cases virus immunoglobulin complexes were detected by using gold-tagged antibodies against human immunoglobulins. Immunoglobulins on the viral envelopes did not interfere with virus typing by immunogold labelling.

Use of gold IgG complexes and human antisera for electron microscopic identification of hepatitis A virus and polioviruses

An indirect immunogold staining technique was used for identification of hepatitis A virus and poliovirus types 1,2 and 3 by electron microscopy. Human convalescent antisera against hepatitis A virus and the three poliovirus types were used as primary antibodies and goat anti-human IgG gold complexes, with an approximate gold granule size of 15 nm, as secondary antibody. Hepatitis A virus was specifically labelled with the homologous antiserum. No labelling was observed when antiserum against poliovirus or other negative control sera were used as primary antibody. Poliovirus types 1, 2 and 3 were specifically labelled with a human serum with high titres of antibody against all three virus types. The use of type-specific antisera made it possible to distinguish types 1, 2 and 3 from each other, although slight cross-reactions occurred. The results indicate that gold IgG complexes in conjunction with human antisera may be used for identification of small spherical viruses.

Immunonegative stain techniques for electron microscopic detection of viruses in human faeces

Immune electron microscopy techniques have for some years been applied to detection of viruses in clinical specimens, especially faecal samples, as both sensitivity and specificity are improved by use of specific antibody. The following review describes in detail different preparation methods and illustrates some of the results that may be obtained.

Development of a sensitive protein A-gold immunoelectron microscopy method for detecting viral antigens in fluid specimens

Protein A-colloidal gold immunoelectron microscopy (PAG IEM) has been employed to specifically detect rotavirus and enterovirus antigen in negatively stained fluid specimens. Unlike other IEM methods, PAG IEM can detect not only viral antigen associated with morphologically recognizable particles but also viral antigens of unrecognizable ultrastructure. This rapid and sensitive immunoassay was found to be applicable to virus-infected stool specimens as well as partially purified virus preparations. The sensitivity of viral antigen detection by PAG IEM was 2- to 40-fold greater than direct IEM and 200- to 1,000-fold greater than direct electron microscopy. In addition, PAG IEM appears to offer a more reliable and sensitive alternative to standard IEM for detection and quantitation of viral antibody.